Negative correlation between dispersal investment and canopy openness among populations of the ant-dispersed sedge, Carex lanceolata

Flowering plants exhibit a wide variation in the resources they invest in dispersal structures (dispersal effort), but the environmental correlates remain unclear in many plants. Canopy openness is predicted to be negatively correlated with dispersal effort, because selective pressures on increased dispersal effort, including host-specific natural enemies and the paucity and/or ephemerality of safe sites, will be more prevalent in shady sites. Here, we tested this prediction using an ant-dispersed sedge, Carex lanceolata (Cyperaceae). By comparing seven populations of C. lanceolata in central Japan, we found a negative correlation between dispersal effort and canopy openness, thus supporting the prediction. A subsequent cafeteria experiment showed that a large species of ant (Formica japonica) with relatively long seed-dispersal distances tended to prefer diaspores with greater dispersal efforts, while smaller ant species with shorter dispersal distances preferred diaspores with lower d...